ok, ladies, help me out here. I have a BFP. I KNOW that I had a period on July 10th. I did not have a "period" again until August 25th. This one consisted of spotting for about an hour and then nothing else. I tested on August 24th and got a BFN. Did not test again after August 25th because I was a goober and thought that was my period. I took a test on Sept 20th and it was VERY positive. Now I am trying to get an estimate of my due date. Can you help me?

I don't go for my first appointment until October 25th and it is driving me nuts not knowing at least a ballpark idea.

I had the EXACT same thing happen with my last baby. I had one day of light spotting, and assumed it was my period, being spastic. It happened on September 19th.
If that HAD been inplantation, Micah would have been due June 5th.
If that had been my last "period", Micah would have been due June 26th.
Of the ultrasounds they gave me, one said June 29th (at 18 weeks), one said July 3rd (at 28 weeks), and the last one said July 2nd (at 35 weeks).
Guess when he was born? July 11th!!!!!!!!!!!!!!!!

So, I don't know WHAT to tell ya. Yours could be implantation, it could've been a mini period, or it could be your body wacking out like mine did, lol!
My second baby was over a week due when we naturally induced, so I am actually more convinced that I did have a mini period, and then my next ovulation was delayed a week, so my US due date of July 3rd was correct...but my body likes to cook babies a little longer in the oven, and so I was a week overdue.

I hope yours is easier to figure out!! I hadn't had regular cycles at that time actually...so if yours have been regular for awhile and you have 28 day cycles, I would really think that it was implantation, and you are due May 11th, 2011!
If it was your last period and you actually got pregnant on your next ovulatory cycle, your due date will be June 1st!

If your bleeding on Aug 25 was implantation bleeding, then we can guess that you concieved on Aug 18, which would give you a due date of May 11. That would go along with a negative test on Aug 25 and a positive Sep 20.